Dysmenorrhea, which may be primary or secondary, is the occurrence of painful uterine cramps during menstruation. In secondary dysmenorrhea, there is a visible pelvic lesion to account for the pain, whereas only a biochemical imbalance is responsible for primary dysmenorrhea. Primary dysmenorrhea affects 50 percent of postpubescent women, and absenteeism among severe dysmenorrheics has been estimated to cost about 600 million lost working hours or over 2 billion dollars annually. Thus, an effective, simple, and safe treatment of primary dysmenorrhea over a period of several days during menstruation will not only enhance the quality of life for sufferers of dysmenorrhea, but will have a positive economic impact.
The pain of dysmenorrhea originates in the uterus. Systemic administration of analgesic drugs generally by the oral route to the patient has not successfully relieved the condition in many women and the administration is frequently limited by side effects. This failure is believed to be the result of a failure to deliver and achieve an effective dosage level of the analgesic to the muscle in the uterus.